Astrophysicist

Tag: meteors

What’s in store for 2024

Happy New Year! I spoke with Glen Hunt on BBC Radio Lancashire this morning about what the Universe (and our exploration of it) might have in store for us this year. It certainly looks like it will be an exciting year for space exploration, and there are many potential discoveries that could be on the cards. Here are some things I’m particularly looking forward to.

The Sky in January

The first thing to look for is the planet Jupiter high in the sky for most of the night. Look towards the South if you are in the northern hemisphere, look to the North if you are south of the equator. Jupiter will be bright, and pretty unmistakable in the early evening.  Look with binoculars, if you have them, to see its moons (and cloud bands, if you’re lucky enough to have access to a telescope).

The ringed planet Saturn is also visible this month, but low in the South-West and fainter. Look with binoculars or a telescope for a view of the impressive ring system.  Saturn sets before 9pm and gets earlier as the month goes on, so catch it early if you can.  There is also a crescent moon close by on the 14th, with both objects low in the South-Western sky.

A sky map showing the locations of some highlights of the January sky.
The sky as seen from North-West England at 6.30pm on January 3rd. Jupiter is high in the South, Saturn is over to the South-West, and the winter favourite constellation of Orion is rising in the East. Image: Stellarium / the author.

If you’re up early, have a look for Venus (easy to spot) and Mercury (quite a lot more difficult!) low in the eastern sky before dawn.  Use binoculars for a better chance of spotting the elusive Mercury, BUT DON’T LOOK AT THE SUN with them!

One of the best meteor showers, but one of the least well-observed (thanks to the weather!), is the Quadrantid meteor shower peaking on January 4th. Unlike most meteor showers which originate from comet debris, this one is due to asteroid 2003 EH1 (possibly a dead comet, possibly a rock comet). This asteroid has an orbit around the Sun lasting 5.5 years, only taking it as far out as Saturn, unlike the majority of comets which spend most of their time beyond Pluto.   Although the body responsible was only discovered in 2003, the meteor shower has been known about since 1825. The radiant, the position the meteors appear to all come from on the sky, was in the now-defunct constellation of Quadrans Muralis (hence the name) – this location is now part of the constellation of Bootes the Herdsman today. 

The Quadrantids can be a very strong shower, with peak rates of more than 100 meteors per hour, but the peak is very short-lived and this year is hampered by daylight during predicted peak hours here in the UK. You have a better chance of seeing good activity from the Americas or Asia this year. Your best chance to view is in the early hours when the radiant is high, after 2am.  Sadly the Moon all rises just after midnight and is half illuminated, making viewing fainter meteors more difficult.  The short predicted peak of activity is between 0900 and 1500 GMT on January 4th.  

The sky looking East at 2.22am on January 4th 2024 showing the constellation Bootes, the location of the radiant for the Quadrantid meteor shower. Image: Stellarium / the author.

The sky later in the year

There will be the usual changing of the constellations as the seasons roll around. Orion is a winter favourite with lots of bright stars and a spectacular star forming region below Orion’s belt that is worth a look with binoculars or a telescope.

There are also a series of meteor showers that happen on the same dates each year as we pass through the debris left behind by comets or asteroids as they orbit the Sun. The ones to watch in 2024, aside from the Quadrantids in January, are the Perseids in mid-August and the Geminids in December. Other meteor showers will happen, but they are not predicted to be as active as these. For most details, keep an eye on the IMO’s Meteor Shower Calendar which is regularly updated.

And a couple of supermoons. While these are not particularly exciting from a scientific point of view, the full Moon is always impressive, and a full Moon at lunar perigee is bigger and brighter than usual, so will be worth a look if the skies are clear. Look up on September 18th and October 17th 2024. (And remember, the astronomical term for this is perigee-syzygy of the Earth-Moon-Sun system. Snappy!)

Spaceflight

2023 was an exciting year for spaceflight and solar system exploration missions, and 2024 is looking like it will be just as exciting. There’s certainly lots planned, both by space agencies like NASA and ESA, governments such as China, and the rapidly growing commercial sector.  Here are some things to look out for in 2024.

Europa Clipper is scheduled to launch in October, heading off to survey Jupiter’s moon Europa, an icy world that may support a sub-surface ocean.  There is a lot of interest in exploring the potential for habitability of Europa (you need liquid water, the right chemistry, and light/heat) and this probe will help with that by allowing scientists to determine the extent of any sub-surface liquid water and examine the geological processes at work.  It won’t arrive until 2030 though, but will complement ESA’s JUICE mission (launched in 2023) nicely when it does.

China plan to launch the next in their series of missions to the Moon with Chang’e 6 heading to the far side of the Moon to attempt the first sample return from the far side of the lunar surface (the side we never see from the Earth).  Likely launch in May.  We have lunar samples from the near side thanks to Apollo, but not from the far side, so comparing the two will tell us more about the history of the Moon.

June should see the maiden flight of the long-awaited Ariane 6, the European Space Agency’s replacement for the long-serving and highly successful Ariane 5 launch vehicle.  It will be able to carry a large payload to orbit, but could lose out commercially to SpaceX’s Starship once that starts flying successfully, and Blue Origin’s New Glenn heavy launcher expecting it’s maiden flight in August. Ariane rockets are expendable, whereas Starship and New Glenn are largely reusable which brings down the cost per launch substantially.

And of course the next Artemis mission taking humans around the Moon for the first time since the Apollo era, pencilled in for November 2024 (but, like all launches, this could slip).  Artemis 2 will be the first crewed flight of the Orion capsule, and see the first humans go beyond low Earth orbit since 1972, taking four astronauts around the Moon and back in what is likely to be a highly-watched mission.  Expect stunning photographs of the lunar surface!

As well as large programmes like Artemis, NASA have also commissioned a series of commercial companies to provide lunar landers for robotic and autonomous probes through the Commercial Lunar Payload Services (CLPS) programme.  The first of these missions, Peregrine 1, is due to launch on January 8th and will carry two rovers, several sensors, and a collection of time capsules. Several other launches are planned, expanding NASA’s existing work with outside commercial contractors that goes back decades.

We are also likely to see both another record year for satellites launched into low Earth orbit (making the risk of collisions ever more likely, and astronomy more challenging) and more new private operators beginning launch operations, including multiple commercial launches to the Moon, adding further competition to the market.

Biosignatures?

And finally (in Jodcast tradition), there is certainly a lot of interest in looking for evidence of biological processes in space, and it’s possible 2024 might be the year we first find solid evidence of biosignatures somewhere other than the Earth. This could be in samples from Mars, or it could come from further afield in the form of spectroscopic signatures from the atmospheres of exoplanets.

Since the 1990s we have discovered more than 5000 exoplanets around stars other than the Sun. The more we look, the more we find. Remember though that this is still challenging – we had the telescope for almost 400 years before we discovered the first solid evidence for extra-solar planets! And as is usually the case with new discoveries, we found the easier ones first.

Astronomers are using powerful telescopes with very sensitive spectrometers to split up the light coming from the exoplanets. This is challenging because a planet only reflects the light from its host star, rather than emitting its own light, so it is much fainter than the star and much harder to detect (which is why it took almost 400 years to find one!). But if you can do it, and split the light into its constituent colours to make a spectrum, you can then look for the signatures of chemicals in the planet’s atmosphere.

Some chemicals are associated with life, so those are the ones to look for. Many of these chemicals can also be produced by non-biological processes too, so finding a signature in the spectrum is only one part of the puzzle in many cases. But if we find one of them, it will certainly be tantalising.

There are also a lot of astronomers looking for signatures of life in the cosmos using a rather different method. Instead of looking for biosignatures, they are looking for technosignatures – evidence of advanced technology from signals that could not be produced in any natural way. This could be radio signals (like the radio and TV transmissions we have been sending into space for many decades now), or something more advanced such as a powerful beacon, or evidence of megastructures, or even evidence of some cataclysmic event.

It may sound like science fiction, but these are genuine research projects. The probability of finding either a bio- or technosignature may be low, but should we find evidence of life elsewhere in the cosmos, the implications really would be tremendous.

That’s not all folks

There are plenty more exciting events to look out for in 2024, from super moons to comets, results from previous missions, new images from JWST that will be as astonishing as ever, and many, many rocket launches. But it’s lunch time here, so I’ll leave it there for now. If you made it this far, thanks for reading! What are you looking forward to this year?

Fireworks? In October?

No, not Bonfire Night. We’re talking celestial firework displays! It’s October, and once again we’re coming up on the time for the annual Orionid meteor shower.

There’s been a trend over recent years of various parts of the media getting a bit hysterical about various astronomical phenomena, and in some cases hyping them up waaaaaay beyond any sensible justification and raising expectations to totally unrealistic levels. So if you’ve arrived here having heard stories about how spectacular the Orionids will be on October 21st, should you believe the hype? TLDR: no, but…

What is a meteor, anyway?

A meteor is actually quite mundane: a small piece of rock, generally smaller than a grain of rice that disintegrates as it flies through our upper atmosphere while travelling at many kilometres per second.

You can see meteors on any clear night of the year, all you have to do is find somewhere dark, look up, and be patient. These are called sporadic meteors and are just the detritus left over from the formation of the solar system, or debris from collisions between rocky bodies in the solar system. In the absence of something like a planet to crash into, they just float gently around in space not doing very much.

Usually you have to wait a while before you see a sporadic meteor, although because they are distributed randomly in space they don’t turn up a regular intervals and you may see a handful close together if you’re lucky.

Meteor showers, on the other hand, can be much more spectacular, and come round predictably at the same time each year. In the case of the Orionids, that time is October 21st – or thereabouts.

Origins of the Orionids

All meteor showers are the result of the Earth passing through regions of space with a higher than average concentration of these dust and rock particles. This happens because stuff gets left behind when comets (and some asteroids) go about their normal business on elliptical orbits around the Sun.

Comets are a bit like giant, dirty snowballs, containing large quantities of both ice, frozen gases, dust and rocks, and other volatile substances. We currently know of more than 3800 comets in the solar system, some of which we have actually visited giving us a much better idea of their chemical composition. Samples collected by the Stardust mission even finding the presence of the amino acid glycine, one of the fundamental building blocks of all life as we know it.

Comets spend most of their lives in the far reaches of the solar system where conditions are very cold indeed. Since comet orbits are elliptical, and centred on the Sun, their orbits also take them into the inner solar system for some of the time.

As a comet approaches the inner solar system it get closer to the Sun and so absorbs more solar radiation, heating the nucleus and causing some of the ice to sublimate – that is it turns directly from a solid ice into a gaseous vapour. As the ice turns to gas, the dust and rock particles embedded in it are released and float away, leaving a trail of debris behind the comet as it travels around the Sun.

 When the path of the Earth happens to cross one of these debris trails, we see an increase in meteors coming through our atmosphere.  This is the origin of a meteor shower, and explains why they are regular with predictable dates of activity.

The Orionid meteor shower is the result of debris left behind by Halley’s comet, one of the most famous comets in our solar system. The comet only returns to our skies once every 76 years (and is not due back until 2061), but the Earth travels through the debris trail each year, giving us the regular Orionid shower in October, and also the less well-known Eta-Aquariid shower in April/May.

Variations

A given meteor shower may not have the same level of activity, year to year. Some years a shower might be fairly unimpressive, with peak rates of only a few per hour. Other years we might have a much larger spike in activity and see rates of several hundred an hour. Rarely we might see rates of more than 1000 per hour – rarely seen meteor storm.

Imagine an aeroplane passing through the sky on a sunny day, leaving a contrail behind it in the sky. If you sit and watch that trail, it slowly expands, becomes less dense, and eventually disappears. Comet debris trails are a little like that (although not as easy to see, being made up of tiny dark particles of rock!).

As that trail ages, it gets less well-confined, the particles move apart slowly. Each time the comet comes round on its orbit, it deposits a fresh trail of denser debris along its orbital path. Add in the fact that the gravitational influence of the likes of Jupiter (and any other planet the comet comes relatively close to) can alter the trajectory of the comet, and you start to get a sense of why the number of meteors we see varies from year to year as the Earth passes though denser or less dense parts of the debris trail.

Very clever folks (such as the IMCCE meteoroids and meteors group) take observational data on the number of meteors observed each year (collected by seasoned observers – and you can help!) and build models of the debris trails for each meteor shower, and use those to make predictions about the number of meteor showers we are likely to see the following year. They are usually pretty accurate, but sometimes we see unexpected spikes in rates that were not possible to predict from past data alone – so it’s always worth a look.

What to expect in 2023

This year we are expecting good observing conditions on the peak night of October 21st, with the Moon at 48% illumination but setting before midnight.  The best time to observe will be after midnight when the Moon sets and the constellation of Orion will have risen – this is the location of the radiant of this shower, the location on the sky the meteors appear to come from, and what gives the shower its name.

Some showers are particularly spectacular with more than one a minute on average.  We’re not expecting that this year for this shower, with predictions of around 20 or so per hour.  However, any shower has the potential to be spectacular, so it’s always worth a look!

The best way to observe is to find somewhere away from street lighting, wrap up warm, and look up!  Obviously, you also need clear skies, but don’t worry if October 21st is cloudy as the streams of debris that cause most meteor showers are wide enough to provide activity over more than one night.  Catching meteors takes patience, but can be worth the effort, and can contribute to citizen science projects.

Clouded out? I expect a lot of us (here in the UK, anyway) will be, thanks to Storm Babet. You might have more luck in other parts of the world. The nice thing about the Orionids is that they are equatorial, meaning you can see them from both the northern and southern hemispheres.

If you do miss them, don’t despair. There are plenty more meteor showers in the calendar!

In December we will see the return of the Geminid meteor shower with a predicted peak of ~150/hour! Much more spectacular! The Moon will also be favourable as it will be very close to the Sun and not up during most of the night, aiding dark sky conditions which help you see the fainter meteors.

So, if you miss out this weekend, make a note in your calendar of December 14th, and make sure you remember to take a look!

© 2024 Dr Megan Argo BEM

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